In general, a video conference system refers to a system enabling people to conduct a conference at a long distance from each other through videos, audios, and the like delivered on monitor screens installed at respective rooms. Video conferencing can not only be conducted domestically but also internationally via satellites, and thus is regarded as cutting-edge technology of great economical merits such as saving costs and time for business travels. A video conference room can be equipped with a number of monitors, TV sets, cameras, microphones, and speakers, as well as electronic blackboards configured to display manually-inputted information to others as it appears, image transmitters, slide transmitters, facsimiles, and the like.
Such a system has a problem in that conference participants, who are joining a conference at a distance, are likely to feel remoteness, and thus requires a device for video and audio coordination so that the participants can feel as if they are in the same space.
Video conference systems have a series of standards recommended by ITU-T (International Telecommunication Union; Telecommunication Standardization Sector), and products have recently appeared which realize conferencing through monitors on personal computers. Conferencing through monitors has an added function for conducting tasks by sharing data composed by personal computers. Data sharing functions include a whiteboard function for displaying an electronic bulletin board on monitor screens of both sides, a function for sharing and using the same application software, and the like. A video conference system using the Internet also has appeared recently. Such a video conference system using the Internet can save movement time taken to join a conference, thereby guaranteeing efficient use of time; it can save relevant costs; it can improve productivity; and it can store video information regarding conference proceedings. There are also provided devices for remote diagnosis or remote education by applying these.
In a conventional video conference system, the server or MCU (Main Control Unit) is configured to receive video signals from a plurality of client systems and remake them into a single video. The size of videos transmitted from the client systems remains the same as initially determined, regardless of the number of persons in conference rooms, until the conference ends, and the server (MCU) changes it to a suitable size through resizing after respective videos are received from the plurality of client systems.
Therefore, it is recommended that, every time the size of videos received from the client systems is changed, the server can change the size, however, this has the following problems: a long initialization time is taken to change the video size, and, if initialization occurs for each video size change, videos are not transmitted for hundreds of milliseconds at minimum, or for more than one seconds at maximum, giving blank screens.
As such, the conventional method of adjusting the video size through initialization is inefficient in that, if a number of client systems transmit video signals simultaneously, the bandwidth of the server increases, it takes an increased time for the server to decode many video signals, and it takes an increased time for the server to adjust the video size.